W. T. Schaller — Supposed Vanadic Acid. 405 



Col. "W. A. Roebling of Trenton, N. J., lias in his collection 

 a specimen of this supposed vanadic ocher from the Cliff mine, 

 Michigan, and has written on the label that this rare specimen 

 of vanadic ocher came from James Nelson of Cold Spring, 

 Putnam Co., N. Y., who bought the collection of Dr. Lee of 

 Pcekskill in 1860. Lee had made a collection of copper min- 

 erals in Lake Superior in 1853, and this original specimen was 

 among them. On request, Col. Roebling very kindly lent the 

 specimen to the writer and it has been possible to identify the 

 material chemically. There seems to be no question but that 

 his specimen is similar to the material tested by Teschemacher. 

 The writer's hearty thanks are expressed to Col. Roebling for 

 his willingness to sacrifice part of the specimen in order to 

 have it determined. 



The yellow to orange mineral encrusts quartz and native 

 copper as felted masses of minute long prismatic crystals, so 

 thin that under the highest magnification, the black borders of 

 total reflection cover the entire crystal. A very few of the 

 largest individuals seem to show a slight transparency in 

 orange color. Chemical tests showed no vanadium and in fact 

 only cuprous oxide could be found. Even water was not 

 found although the minute amount of material available made 

 the test of doubtful value, as a small amount of water 

 may have escaped detection. Treatment with HC1 turned 

 the mineral white, doubtless due to the formation of cuprous 

 chloride. Comparative chemical tests with the hydrocuprite 

 from Cornwall, Lebanon County, Pennsylvania, gave identical 

 tests and the supposed vanadium ocher from Lake Superior is 

 probably the same as the hydrocuprite from Pennsylvania. 

 Possibly the Lake Superior material has changed from a col- 

 loidal hydrocuprite to crystalline cuprite and would then be a 

 meta-colloid as recently defined by Wherry.* 



In the original description of hydrocuprite,f Genth states 

 that : " the cuprite variety chalcotrichite from Cornwall [Penn.] 

 sometimes assumes an orange color, so that on the same piece 

 acicular crystals of a fine crimson color can be seen gradually 

 changing to an orange yellow. It is, therefore, very probable 

 that the orange crystals are pseudomorphs of hydrocuprite 

 after cuprite." According to Genth the direction of the reac- 

 tion Cn a 0.wH a O^Z^Cu a O+nH a O is the reverse for the Penn- 

 sylvania hydrocuprite to what is suggested for the Lake Supe- 

 rior material. Under the microscope, the Pennsylvania hydro- 

 cuprite is seen to be formed of very small prismatic crystals 

 similar to those of the Lake Superior material but not so 

 minute. 



* Wherry, E. T., Journ. Wash. Acad. Sci., vol. iv, p. 112, 1914. 

 f Genth, F. A. , Preliminary report on the mineralogy of Pennsylvania, 

 Second Geol. Survey Penn., p. 46, 1875. 



